The present invention relates generally to agricultural machinery and, more particularly, to improvements to means and methods for detecting cultivation boundaries or other guide variables. The invention concerns contactless detection that may be used to guide the agricultural machine.
An apparatus of this kind is known from German Patent 2 455 836. The apparatus disclosed therein features a transmitting and receiving unit which detects an edge of crop material in the front of the agricultural machine, in the direction of travel, without contact and at an acute angle to the crop. The reflection signal generates a steering signal by several different evaluation methods. The transmitting unit works with narrow-band light sources, such as polarizers and modulators, and short-wave highly focused electromagnetic waves or sound waves. The reflected signals are compared with a nominal value and fed to an automatic steering device. Consequently, the lateral distance between the edge of the cutting mechanism and the edge of crop material is minimized. To detect the edge even more precisely, the apparatus is periodically pivoted about an approximately vertical axis and generates the position of the edge corresponding to a nominal value, based upon the average of the reception signals.
The disadvantages of this apparatus include the mounting on the machine and the method for evaluating the sensor signals. The layout of the disclosed apparatus is suitable only to a limited extent for detecting the edge of a standing crop. The scanning beam is reflected laterally by the edge of the standing crop and the distance from the edge is determined from the received signal. Unevenness of the ground or reduced height of the standing crop may cause the apparatus to determine the distance from the ground or above the standing crop, rather than from the crop edge, requiring fine adjustment and exact maintenance of the scanning location at the edge. These measures are very expensive. Variable quantities known in the art such as the height of standing crop, the working height, variations in inclination of the machine and terrain, together or individually, significantly influence the signal received.
An alternative disclosed evaluation means may be selected to improve the evaluation, wherein the transmitter is pivoted about a vertical axis. However, such an apparatus works satisfactorily only when the degree of reflection is constant at and around an edge of the standing crop. Such optimum working conditions are rare and hence a satisfactory work result is rarely achieved.
When the apparatus is used for different types of edges or cultivation boundaries, where the same reflection conditions prevail on both sides of the boundaries, such as for example on a plowed furrow, the measurement of distance fails because only a dual-mode control circuit can be accomplished, which is known to lead to an inadequate work result. Furthermore, pivoting the transmitter about a vertical axis does not improve the measurement. Irrespective of the method of evaluation selected, the average measurement depends on the degree of reflection and the width of the track, and does not reveal the position of the track relative to the implement. Therefore, the apparatus and evaluation of German Patent 2 455 836 are of limited utility in detecting a cultivation edge.
A self-steering device is disclosed in German Patent application 1 95 08 942.1 where a locating device is arranged at a distance above the grain or crop in such a way that the locating signals locate the cultivation edge obliquely from above, approximately perpendicular to the blade of the cutting mechanism. Various locating signals and signal evaluations are disclosed and the cultivated and uncultivated field areas are detected by a locating device via an ultrasound beam or a laser scanner. In a particularly simple embodiment, dual-mode control is accomplished by two laser partial locating beams.
The evaluation of the reception signals is a significant drawback of this particular type of locating device. A laser scanner can be used only for detecting an edge or track which can be detected in the height profile. At frequently occurring storage points in th standing crop, the system fails. Furthermore, to prevent exceeding the maximum working width of the laser beam requires maintenance of a roughly constant scanning distance. When using an ultrasound locating device, the evaluation methods described depend upon the quality of the reference variable. The evaluation and generation of control signals for an automatic steering system requires the capability to evaluate the echoes with the aid of a reference variable. However, this reference variable is not a constant and would have to be varied along the crop edge. The locating device, therefore, delivers satisfactory results for detecting an edge only piecemeal and with high expenditure on correction. However, there is no aptitude for use of the d vice at other kinds of cultivation boundaries.
A further locating device is disclosed in German Patent application 1 95 08 941 in which three partial locating devices are arranged on an agricultural machine. The first locating device is directed onto the harvested field, the second locating device is directed onto the unharvested field and the third locating device is directed onto the edge of the crop material. The reference variable for the third partial locating device is derived from the average of the locating signals of the first and second partial locating devices.
It is a disadvantage for this particular device that the echo of the partial locating signals greatly varies and, thus no satisfactory following of the edge is allowed. The crop density, scanning distance and crop or stubble height affect the partial locating echoes. Necessary integration and averaging of several measurements make it impossible to react to rapid variations in the echo, which can even occur in opposite directions, in such a way that reliably detecting and following the edge is possible. The triple construction of the locating device is also very cost-intensive and requires special synchronization of the transmitting signals. Moreover, this device is unsuitable for locating swathes of crop material. The reference variables determined by the outer partial locating devices do not represent the reference variables needed. The middle partial locating device must be positioned over a swathe in such a way that the beam center lies over the swathe center. This positioning is of course possible, but no edge signal can be generated by the device at the swathe center. A variation in the echo of the middle partial locating device takes place only after the locating beam leaves the swathe of crop material. For detection of a plowed furrow, a partial locating device would be required to determine a reference variable of the bottom of the furrow. However, this is not possible because of the width of the ultrasound beam.
From East German Patent 264 366 another contactless operating locating device is known, which is arranged above the crop edge and converts reflected optical radiation to an electrical position-related signal. The temporarily stored values are then evaluated in an information system according to color or gray stages and converted to a steering signal.
An optical system with this kind of evaluation basically has the drawback that due to different directions of exposure, shadows arise, which are difficult to be distinguished from the crop edge. Furthermore, the arrangement and/or location of attachment has an adverse effect on the steering control circuit due to the small lead. Also, the device is unsuitable for detecting different edges and cultivation boundaries. Often the color variation between cultivated and uncultivated field areas is extremely minimal. Furthermore the accuracy of the device is determined by the number and size of receiving elements and, with sufficient resolution, results in high costs.
Another device is known from German Patent application 197 26 917.6, which corresponds to U.S. application Ser. No. 09/103,431. It discloses a scanning device for detecting contours extending over the ground. A laser scanner attached to a harvesting machine scans the contour by distance measurement in front of a harvesting machine. Changes in distance are determined from the contours and are assigned to a scanning angle. At the point of maximum distance variation a steering difference is determined relative to the associated scanning angle and fed to an automatic steering system.
For use of the device along a swathe, the value with the minimum distance is selected from the measured values as a guide variable. However, this device is suitable only for detecting cultivation boundaries which have a change in height profile. This device fails for cultivation boundaries which do not have these changes, such as at storage points in the standing crop or at soil cultivation boundaries.
It is a general object of the present invention to overcome one or more of the above-described deficiencies.
An object is to provide an apparatus and method which allow reliable detection of the cultivation boundary, below a boundary between a cultivated area, such as an edge of crop, stubble field, freshly loosened soil, wilted material or turf, or a mown edge and the adjoining uncultivated area.
Another object is to provide a device and method which allow the reliable detection of a guide variable.